In sugar beet harvesters, the lifter wheels for lifting the sugar beets from the ground are attached to a strut, which is secured to the tool bar of the harvester. During the harvesting operation, the lifter wheels sometimes strike buried objects, such as rocks or the like, which exert a vertical torque on the strut, and which can result in damage to the lifter wheel assembly.
Attempts have recently been made to permit the lifter wheels and associated strut to yieldably pivot upwardly in response to striking a buried rock, to avoid damage to the assembly. For example, U.S. Pat. No. 4,137,973 discloses a lifter wheel assembly provided with coil springs positioned forwardly of the tool bar and serving to permit upward pivoting movement of the strut and lifter wheels when the latter strikes a buried rock. The lifter wheel strut is connected to a mounting bracket by a fixed pivot and underlies the tool bar. The lifter wheel assembly can pivot in only one direction with respect to its normal operating position.